In this document
If you are only interested in the kernel, you may use this guide to download and build the appropriate kernel.
The following instructions assume that you have not downloaded all of AOSP. If you have downloaded all of AOSP, you may skip the git clone steps other than the step to download the actual kernel sources.
We will use the Pandaboard kernel in all the following examples.
Figuring out which kernel to build
This table lists the name and locations of the kernel sources and binaries:
|Device||Binary location||Source location||Build configuration|
You will want to look at the git log for the kernel binary in the device project that you are interested in.
Device projects are of the form device/<vendor>/<name>.
$ git clone https://android.googlesource.com/device/ti/panda $ cd panda $ git log --max-count=1 kernel
The commit message for the kernel binary contains a partial git log of the kernel sources that were used to build the binary in question. The first entry in the log is the most recent, i.e. the one used to build that kernel. You will need it at a later step.
Identifying kernel version
To determine the kernel version used in a particular system image, run the following command against the kernel file:
$ dd if=kernel bs=1 skip=$(LC_ALL=C grep -a -b -o $'\x1f\x8b\x08\x00\x00\x00\x00\x00' kernel | cut -d ':' -f 1) | zgrep -a 'Linux version'
For Nexus 5 (hammerhead), this can be accomplished with:
$ dd if=zImage-dtb bs=1 skip=$(LC_ALL=C od -Ad -x -w2 zImage-dtb | grep 8b1f | cut -d ' ' -f1 | head -1) | zgrep -a 'Linux version'
Depending on which kernel you want,
$ git clone https://android.googlesource.com/kernel/common.git $ git clone https://android.googlesource.com/kernel/x86_64.git $ git clone https://android.googlesource.com/kernel/exynos.git $ git clone https://android.googlesource.com/kernel/goldfish.git $ git clone https://android.googlesource.com/kernel/msm.git $ git clone https://android.googlesource.com/kernel/omap.git $ git clone https://android.googlesource.com/kernel/samsung.git $ git clone https://android.googlesource.com/kernel/tegra.git
goldfishproject contains the kernel sources for the emulated platforms.
msmproject has the sources for ADP1, ADP2, Nexus One, Nexus 4, Nexus 5, Nexus 6, and can be used as a starting point for work on Qualcomm MSM chipsets.
omapproject is used for PandaBoard and Galaxy Nexus, and can be used as a starting point for work on TI OMAP chipsets.
samsungproject is used for Nexus S, and can be used as a starting point for work on Samsung Hummingbird chipsets.
tegraproject is for Xoom, Nexus 7, Nexus 9, and can be used as a starting point for work on NVIDIA Tegra chipsets.
exynosproject has the kernel sources for Nexus 10, and can be used as a starting point for work on Samsung Exynos chipsets.
x86_64project has the kernel sources for Nexus Player, and can be used as a starting point for work on Intel x86_64 chipsets.
Downloading a prebuilt gcc
Ensure that the prebuilt toolchain is in your path.
$ export PATH=$(pwd)/prebuilts/gcc/linux-x86/arm/arm-eabi-4.6/bin:$PATHor
$ export PATH=$(pwd)/prebuilts/gcc/darwin-x86/arm/arm-eabi-4.6/bin:$PATH
On a linux host, if you don't have an Android source tree, you can download the prebuilt toolchain from:
$ git clone https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/arm/arm-eabi-4.6
As an example, we would build the panda kernel using the following commands:
$ export ARCH=arm $ export SUBARCH=arm $ export CROSS_COMPILE=arm-eabi- $ cd omap $ git checkout <commit_from_first_step> $ make panda_defconfig $ make
To build the tuna kernel, you may run the previous commands replacing all instances of "panda" with "tuna".
The kernel binary is output as: `arch/arm/boot/zImage` It can be copied into the Android source tree in order to build the matching boot image.
Or you can include the
TARGET_PREBUILT_KERNEL variable while
make bootimage or any other make command line that builds a
$ export TARGET_PREBUILT_KERNEL=$your_kernel_path/arch/arm/boot/zImage
That variable is supported by all devices as it is set up via device/common/populate-new-device.sh